Detection of the soil-rock interface based on microtremor H/V spectral ratio method: a case study of the Jinan urban area

The soil-rock interface plays an important role in urban earthquake resistance and engineering construction of the underground. The various interference in the city limits the use of traditional geophysical exploration methods. This paper presents a study on the soil-rock interface of the Jinan urban area using the microtremor H/V spectral ratio method, which is environmental friendly and has strong anti-interference ability. Microtremor measurement was carried out in the downtown area of Jinan, and the microtremor signals of more than 400 measuring points were obtained, and the corresponding H/V spectral ratio curves were calculated. These H/V curves are divided into four types: single peak, broad peak, double peak and flat curves. The relationship between different types of curves and geological structure are analyzed. The bedrocks of the study area are divided into two types according to its characters, limestone and magmatic rock. The depth-frequency relationship of bedrock limestone is summarized. It is also found that when the bedrock is magmatic rock, such a relationship cannot be obtained. According to this relationship, the depth of the soil-rock interface of some lines in Jinan is calculated. In addition, the calculation results are in good agreement with the borehole data, which can meet the accuracy requirements of engineering detection. This method provides a fast and accurate solution for determining the depth of the soil-rock interface in urban areas with strong disturbance.